In some motor vehicles, an air outlet is located in the rear quarter of the body of the motor vehicle. However, in some instances, noise and vibrations may enter the cabin via the air outlet. Modern vehicles may also include modern electronic measures to aid the driver such as a blind spot indicator (“BSI”) sensor located in the rear quarter of the body of the motor vehicle. A cover is necessary to protect the BSI from false readings caused by dirt and snow interference. There is a need to provide an underbody cover assembly to protect the BSI that also prevents noise and vibrations from entering the cabin.